op {
  name: "TensorListConcatLists"
  input_arg {
    name: "input_a"
    type: DT_VARIANT
  }
  input_arg {
    name: "input_b"
    type: DT_VARIANT
  }
  output_arg {
    name: "output"
    type: DT_VARIANT
  }
  attr {
    name: "element_dtype"
    type: "type"
  }
}
